Radio Frequency (RF) antennas are becoming more prevalent in a wide variety of portable computing devices, such as cell phones, personal data assistants (PDAs), and handheld devices such as Radio Frequency Identification (RFID) readers. In Ultra High Frequency (UHF) applications, RFID is becoming more and more popular in the field of contactless identification, tracking, and inventory management. UHF RFID is currently replacing the more traditional portable barcode readers, since use of barcode labels have a significant number of disadvantages such as: limited quantity of information storage of the product associated with the barcode; increased amounts of stored data by the barcode is becoming more complicated due to the limited number of lines and/or patterns that can be printed in a given space; increased complexity of the lines and/or patterns can make the barcode label hard and slow to read and very sensitive to the distance between the label and reader; and direct line-of-sight limitations as the barcode reader must “see” the label.
However, there are significant disadvantages with the current state of the art for miniaturization of antennas, in view of the ever increasing desire for smaller and more complex portable computing devices. It is recognised that as the size of the portable computing device is decreased, the amount of available space in the housing of the portable computing device becomes a premium. Also, as more and more device features are included in today's portable computing devices, there is less room available in the housing to position all of the desired device features.
However, miniaturization of antennas can come at a cost of decreased antenna performance, e.g. antenna gain and general antenna efficiency. It is recognised that by using high dielectric constant materials between the antenna conductors, the antenna footprint can be reduced but at an expense of antenna thickness, i.e. an increased thickness of dielectric materials between the antenna conductors can be a result of decreased antenna footprint. However, excessive thicknesses of dielectric materials can result in an undesirable decrease in the dielectric constant exhibited by the dielectric material, which results in an overall undesirable decrease in the gain of the antenna.
Further, higher dielectric materials are typically more expensive than lower dielectric materials, so the added cost of material used in the manufacture of miniaturized antennas can become an issue.